The present invention relates to an image processing method, a storage medium, an image processor and-an image recorder. More particularly, this invention relates to an image processing method and an image processor for providing predetermined processing to photographed image data and for generating an image signal for producing preferred output, and an image recorder for providing predetermined processing to photographed image data and for generating an image signal for producing preferred output.
When the photographed image data is printed on a medium, the photographed image data is provided with predetermined image processing in order to ensure that favorable impression is given to the person viewing the image printed on the medium.
With recent advances in input media, there has been a growing demand for more improved image quality while favorable impression of the photographed image is kept unimpaired.
In the processing of photographed image printed on the film, the Japanese Application Patent Laid-Open Publication No. Hei 11-317863 discloses a method for faithful reproduction of the image having an impression close to an actual scene captured human eyes by dodging treatment plus blur masking through the use of color reproducing parameters of the major region and background region included in the image. The Japanese Application Patent Laid-Open Publication No. Hei 11-191871 proposes a similar art regarding the processing of photographed image to be printed on the film, i.e. a technique for compression processing of the image dynamic range calculated on the basis of photographic information and subject region.
The Japanese Application Patent Laid-Open Publication No. Hei 09-233423 proposes a technique of image processing by extracting the image region of the human face from the image obtained film, and by changing edge enhancement or contrast based on the size of the extracted human face image region. Further, the Japanese Application Patent Laid-Open Publication No. 2000-16874 proposes a technique of ensuring a high-quality picture quality on the same level as that of the picture in printing the image captured by a digital camera, by customized image processing according to the image processing conditions for each model in conformance with the characteristics of a particular camera model, and by reflecting the gray scale for a specific subject and color taste, thereby setting color gradation without dependence on camera model.
The Japanese Application Patent Laid-Open Publication No. 2001-5960 discloses a technique wherein, based on the edge-enhanced data obtained by edge detection of a digital image, sharpness is enhanced in the target region, and unsharpness mask coefficient is changed from the subject region in other regions so that a composite image is formed. This step prevents enhancement of subject sharpness and accompanying unwanted edge enhancement on the background are avoided, with the result that a photograph-like image is ensured. Similarly, the Japanese Application Patent Laid-Open Publication No. Hei 11-339035 proposes a mask image processing technique where the degree of reducing the enhancement of high frequency component or middle frequency component is adjusted according to the size of the human face in the processing of an image including human face image.
In recent years, however, generating means for generating the photographed image data have been diversified, and include a wide range of types such as a less costly digital camera for toy, lens shutter digital camera, high-quality single lens reflex digital camera, film scanner, flood bed scanner and many others. The media for issuing image signals have also been diversified to include a silver halide digital printer, ink jet printer, thermal printer, sublimation printer and electrophotographic printer. The size of the image produced therewith has also been diversified to cover from a several-inch square seal image to a poster-sized image. Further, as the photographed image data is sent and received from the Internet or the like, there have been an increasing number of problems where image signals with the medium size beyond the expectation of the camera user are issued. Under such complicated circumstances, it has become difficult for the prior art technique to send an image of favorable impression to media.
For example, the technique disclosed in the Japanese Application Patent Laid-Open Publication No. Hei 11-317863 is insufficient due to inadequate image because the contrast of the image portion of the under-subject in reverse-lighted scene is unduly increased, and excessive granular incompatibility is felt in the background. Further, the techniques disclosed in the Japanese Application Patent Laid-Open Publication Nos. Hei 11-191871 and 09-233423 is difficult to put into practical use, because deterioration of granularity is caused by inadvertent contrast processing, and natural continuity of intermediate colors cannot be reproduced, with the result that incompatibility is felt in the background.
In the technique introduced in the Japanese Application Patent Laid-Open Publication No. 2000-16874, the image processing is greatly affected by the operator decision. When image processing is performed in an automatic mode, it is unrealistic and impracticable to update the data in conformity to diversifying input media models and output methods. If put into practical use, it is not always possible to ensure high quality image processing with the feeling of the original scene kept intact. For this reason, this technique is still insufficient at practical level.
According to the technique introduced in the Japanese Application Patent Laid-Open Publication No. 2001-5960, inadvertent edge enhancement is performed although a human and still object are included in the subject, with the result that details of the dress is subjected to edge enhancement despite satisfactory face of the subject. In this respect, this technique is still insufficient at practical level. Further, the texture of a still subject is impaired, for example, by the presence of a metal and a natural object. This gives rise to unnatural continuity with the background and damages the feel of the original scene.
In the technique disclosed in the Japanese Application Patent Laid-Open Publication No. Hei 11-339035, the image processing parameter is changed by the size of the human face alone. This signifies a heavy dependence on the scene, and image qualities are different despite continuous photographing in the same environment. In this respect, this technique fails to provide a stable and high fidelity representation of the atmosphere of the original scene.